Alloy



Patented Aug. 7, I934 ALLOY Robert H. Leach, Fair-field, Conn assignorto Handy & Harman, New York, N. Y., a corporation of New York NoDrawing. Application June 10, 1932, Serial No. 616,498

4 Claims. (Cl. 75-1) This invention relates to silver alloys and .is inthis group have that effect. All the metals in concerned moreparticularly with a novel silver the group, however, do increase thetarnish realloy which may be used to especial advantage in sistance to agreater or less degree. Of the several the manufacture of table silverand hollow ware metals mentioned for use as hardeners, I prefer and forvarious other .purposes, because it has the to use nickel, as it offerscertain advantages over property of strongly resisting tarnish anddiscolthe others in the group.v However, for the puroration. pose forwhich these metals are used in the new As is well known, silver alloysof ordinary comalloy, all four metals are substantial equivalents.positionandcontainingcopper as the base ingredi- Silver alloys which arenow in widest use areent are susceptible to tarnish. Such discolorathoseof sterling fineness containing not less than 65 tion of the metal isbrought about by numerous 925 parts of silver per thousand, and inproducagents, the most active being sulphur which is ing the new alloyof sterling fineness, I use appresent in various foods such as eggs, andis also proximately 92.5% silver, cadmium ranging from present to someextent in the atmosphere in the about 3% to about 4%, tin ranging fromabout form of gaseous compounds. Sulphur in both 3% to, 4 /g%, and asmall amount of nickel, sili- 70 forms causes tarnishing at a rate whichdepends con, antimony, and/or magnesium as a hardener, on the length ofcontact or exposure of the nickel and/or silicon being especiallydesirable as metal, the concentration of the sulphur in the hardeningingredients. When any one of the food, or air, and the form in which thesulphur is hardening metals is used, the amount present is present. Inany event, the necessity of frequent from about 4% to not to exceedabout 1%, but 76 cleaning and polishing of silver articles to keep whentwo or more are employed, the total amount them in bright condition hasled to numerous of the hardening ingredients is not to exceed attemptsin the past to produce silver alloys which about 1.5%. are of goodappearancahave the desired work- Instead of using cadmium as an elementin the ing characteristics, and have a better resistance new alloy, Ihave found that approximately the 80 to tarnish than ordinarysilver-copper alloys, same results may be obtained if zinc besubstituted but up to the present, the proposed alloys with for part orall of the cadmium. I prefer to use which I am familiar, have not provenentirely satcadmium, however, and believe that the resistance isfactory.to tarnish of the new alloy in which cadmium is 80 The problem ofproducing a silver alloy which used instead of zinc is somewhat greaterthan that is resistant to tarnish is a difflcult one because inof analloy in which zinc is present. vestigation has shown that binary alloysoffer Typical examples of the new alloys of sterling little promise andthe number of ternary and fineness have the following approximateanalyses: quarternary alloys is very large. When it is un- 35 iierstoodthat small variations in the ingredients Example 1 in these alloys havean important effect on the re- Per cent sistance to tarnish and theamounts of the alloy- Silver ing ingredients used are highly criticalwith re- Cadmium spect to tarnish resistance, themagnitude and Tm 40difficulty of the problem will be appreciated. Nickel 95 As a result ofmy investigations in this field, I Example Na 2 have found that a silveralloy which has excellent Per cent resistance to tarnish produced byvarious agencies Silver 92 5 may be produced by using cadmium and tin asa;

45 alloying metals, provided the cadmium and tin are Tin T confinedwithin rather narrow limits, and the new gs; alloys may be given asomewhat improved resist- Nickel ance to tarnish and, in some casesbetter physical properties, if a small amount of a fourth ingre- ExampleNo. 3

50 dient is added, which may be one or more of the Per cent metals,nickel, silicon, antimony and magnesium. Silver I 92.5 In mostinstances, the fourth ingredient has a Cadmium. 3,0 slight hardeningeffect and I shall, therefore, Tin 3,0 refer to it as a "hardener,although it is to be Nickel 0,5

55 derstood that not all of the metals mentioned Magnesium 1.0 1 0 T1Nickel, antimony, magnesium, or silicon Example No. 4 I

Per cent As above mentioned, zinc may be substituted for all or part ofthe cadmium in the 800 fine alloy, but I prefer to employ cadmium.

I am aware that it has been proposed heretofore to make silver alloyswhich contain zinc, antimony, and tin, and tin and chromium, but after alarge number of experiments involving the exposure of these alloys tovarious forms of tarnish, I have found that the ranges of cadmium andtin and the relative proportions used are quite critical and anysubstantial departure from the ranges given results in a lowered tarnishresistance. My tests indicate further that increasing the cadmiumcontent improves the resistance of the alloy to certain forms of tarnishwhile increasing the tin improves the resistance to certain other formsof tarnish. An alloy which has the best resistance for tarnish from allsources is one in which the cadmium (or zinc) and tin are present inamounts within the ranges specified for an alloy of sterling fineness.

What I claim is:

1. A silver alloy which comprises silver ranging from about to 92.5%,cadmium ranging from about 14.5% to about 3%, tin ranging from about 5%to about 3% and nickel ranging from about 0.25% to about 1%.

2. A silver alloy which comprises silver ranging from about 80% to about92.5%, cadmium ranging from about 14.5% to about 3%, tin ranging fromabout 5% to about 3% and about 0.5% of nickel.

3., A silver alloy of sterling fineness which comprises about 92.5% ofsilver, from about 4% to 3% of cadmium, from about 4.5% to about 3% oftin, and from about 0.25% to about 1% of nickel.

4. A silver alloy of sterling fineness which comprises about 92.5% ofsilver, about 3.5% of cadmium, about 3.5% of tin, and about 0.5% ofnickel.

ROBERT H. LEACH.

